ronk wrote:Neither exposes a "singles backdoor" like daj95376's chain, but the two bivalues created can then be used in a long (13-node) xy-chain for r1c7<>6.

Wow ronk, that's one impressive XY-Chain from [r1c8] to [r6c7] ... resulting in [r6c8]<>6 as well. Since it connects diagonal cells in an X-Wing, it also forcing the endpoints of the XY-Chain to be 6. Lots of action in your XY-Chain